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Observation Coverage

Precise measure of verification progress and coverage improvement

An effective measure of verification progress, including untested design area guidance, requires a precise view of test coverage achieved. Verification sign-off without clear quality metrics raises the specter of post-production device bugs. However, common coverage measures, based on the design code being activated during simulation, are inadequate as the only quality indicator. 

OneSpin’s Quantify Fault Observation Coverage technology provides precise, accurate verification coverage measurement for formal verification, far surpassing other techniques in use today. 

Formal Verification Coverage

Common coverage measures, based on the design code being activated during simulation, are inadequate as the only quality indicator. A more effective approach is to check that any design problem will be observed by the verification environment, but the few available techniques, such as cone-of-influence, prove coverage or general mutation coverage are inaccurate or too slow to execute. 

OneSpin’s patented Quantify technology employs observation coverage, which evaluates the effectiveness of a set of assertions being triggered by incorrect behavior in the design code. The algorithm ensures high accuracy with superior performance compared to earlier methods, such as reachability, cone-of-influence, and mutation-based analysis.

In addition, Quantify analyzes the reachability of design structures in simulation and formal verification flows, checking that code has been stimulated, or identifying reasons why not. It provides clear and concise measurements of overall progress, as well as specific direction towards untested code elements. 

Quantify has two use modes. In the first mode it highlights code areas requiring coverage improvement, targeting further test development. In the second mode, the tool will provide a range of valuable metrics, demonstrating across a design the level of reachable code and coverage achieved for various design partitions, qualifying the verification environment for verification sign-off. 

Improving Verification Quality and Measuring Progress

Employing a simplified use-model, and requiring no changes to code or assertions, Quantify produces a range of cumulative metrics allowing for the rapid assessment of verification progress as well as guided test improvement directives. The automated detection of unreachable and redundant code enhances the analysis. Quantify may be used within existing environments regardless of verification tooling. The tool operates with standard HDLs, SystemVerilog and PSL assertions, and may be easily integrated with coverage databases, including the UCIS standard.

Improving Simulation Coverage

Quantify may also be used to measure Reachability Coverage for both formal and simulation based verification environments. In this mode, the tool will test the design code for areas that may not be reached and often indicating problems, for example, dead code that is disconnected from design inputs or redundant code. It will evaluate for over-constrained test environments indicating potentially untested code areas. If code can be reached, it will also evaluate if it actually was reached during simulation. The combination of Reachability and Observation Coverage provides an accurate measure towards verification closure.


Quantify is included as part of OneSpin 360 DV-Verify which enables a complete, coverage-driven verification flow, allowing the rapid convergence of the verification process. It may also be used with simulation and formal verification tools from other suppliers as an independent coverage arbiter. It provides:

  • Unprecedented coverage precision, leveraging patented Observation Coverage algorithm
  • Push-button integration with simulation for reachability analysis and test vector generation
  • Guided test development with instant feedback on assertion quality and verification holes
  • Industry proven verification sign-off analysis and integration with coverage databases

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Measure your formal verification coverage precisely and avoid costly verification holes. Try Quantify and OneSpin 360 DV-Verify now!

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